This invention relates to forced air heaters, and more particularly to improvements in the portable forced air heater shown in my U.S. Pat. No. 3,781,165. This heater is particularly useful for supplying heated air in locations where electrical and/or mechanical power is not readily available. It is designed for use with fuels such as propane and butane, which can be stored under pressure as liquids at room temperature, but which are self-pressurizing and automatically supply the fuel as a pressurized gas. This eliminates the need to pressurize the fuel in order to drive the pneumatic motor which drives the heater fan or blower, thus providing a highly efficient, portable and inexpensive forced air heater.